When talking about photography, it is usually said that photography captures a moment in time. this statement is a paradox. When setting up your camera to take a picture, you must calculate the exposure by setting two things, firstly the aperture and secondly the shutter speed. Shutter speeds are measured by the second or a fraction of it. Because of this photography can capture more than a moment and less than a moment depending on your interpretation.
Taking advantage of the paradox can create images that visibly show the movement of time. The technique of creating these images is called motion blur. Motion blurred objects is different from out of focused objects. Motion blur is the blur of objects in motion. Motion blurred pictures are most commonly associated with sports photography of fast moving subjects. But motion blur can be used for a variety of pictures and once mastered can be a useful tool in your photographic belt.
Motion blur is best created in camera but you can also do it in Photoshop.
Traditional Motion Blur
To take a motioned blur shot you will need you camera hopefully with some kind of shutter control and a tripod. I would normally tell you to switch to your cameras manual mode but if you are taking a series of images and want to have the same shutter speed in each picture then I would recommend that you use the SP (shutter priority) mode. This mode keeps the shutter speed at whatever you select it to be and automatically changes the aperture to give the correct exposure.
Choosing the shutter speed depends on your subject. If your subject is moving slowly, then you will need a very slow shutter speed than if it is a fast moving object. The most import thing is that your shutter speed is slower than the subject.
Issues of long exposures
When you have a long exposure you are letting more light into the camera. During the day this can cause your image to become over exposed. One way to reduce the exposure is by changing the aperture to a higher setting like F22 though this will mean you have a very wide depth of field. If you are using the Sp mode then this shouldn’t be a problem. If you are at the end of your aperture range you can also lower the ISO you are shooting on to 80ISO.
Another issue can be that the highlights are blown out in your image. One solution is a neutral density filter (ND filter) which will also lower the amount of light coming onto your sensor of film. If you are taking landscape images it might be worth using a Gradient ND filter. This is a filter which has a smooth gradient coating from a strong ND filter to none at all. You can put it on your camera to control where the effect of the filter is on your image. This filter is also brilliant if you want to have a dark sky and lighter foreground to the horizon.
These problems are common when shooting during the day. At night you will have fewer problems but your exposures will be longer which may cause an issue if your camera does not have a bulb (B) mode.
Keeping sharp and blurred
A great thing about motion blur is that you can mix your subject being sharp while its motion is blurred at the same time. One way to do this is to use a flash to freeze the object. With a long exposure you can use the flash to suspending the subject in the camera while the rest of the movement continues.
If you don’t have a flash another approach can be to pan the camera with moving object. To make this work effectively you must move your camera at the same speed as the object and keep it in the same position of your frame. Since you are moving the camera at the same speed as the subject there is no blur occurring with your subject but the area around your subject will blur with the motion.
Water is one of the most common pictures taken with motion blur turning the movement of the tide or the speed of a river and a water fall, becoming milky white.
Fire is also a great subject as it becomes liquid with the longer the exposure.
Subjects on a carrousel; the spinning movement of the carrousel while your subject is sharp.
Movement in the city; using people and cars to show the busyness of a city. The cars will create long lines of light tracing around the streets where as people become ghost next to the static buildings.
The sky. Using a long enough exposure you can create fast moving skies on a still landscape.
The digital faux
Creating a digital motion blur can be easy and cheap or a little bit harder and look more authentic. Before doing a digital alternative it is always good to take some pictures traditionally so you know what the feel of the image is.
First import the image and make a duplicate of the layer.
With the duplicate layer selected go to your filters menu and select blur and then motion blur. Before playing the dialogs you need to think about the direction of the suposed movement and how fast you think it is moving and then change the settings as you need them to be changed. Don’t try to make the blur too big as it may look unnatural.
Once the filter has been done you need to play with layer masks. I have two ways of working with the layer masks.
If you are new to Photoshop continue reading (if not skip this part.)
Select a layer mask form the layers menu, next select the brush tool and a soft brush.
Make sure the colour black is selected, click on your layer mask and paint the unblurred image underneath. Once you have exposed the image you are done.
I tend to take a longer route and those with layers experience may prefer this way. I will select the pen tool and trace the subject on the unblured layer.
Once I have finished the trace I right click and turn it into a section. With the selection on I click onto the blurred layer and create a layer mask, this will transfer the section onto the mask.
I then duplicate the blurred layer with a layer mask hide all, and paint on the edges of my subject a small amount of blur. For me this creates a more realistic blur effect that just painting it on.
If the image is of a vehicle there needs to be two areas of motion blur since the wheels are spinning and the forward motion of the car/bike. This means you will need to make two separate blurs and then blend them together.
Whatever methods you use have fun when taking your pictures.